Method
> If your leeks are raw, steam them for 15 minutes then open them in half lengthways and remove the center part of the leeks (this is quite a delicate operation!). Cut the removed flesh into small chunks.

> Melt 20g of butter in a frying pan, add the thinly sliced onions and leave to sweat over a low heat. Once tender, increase the heat and add the ceps. Leave to cook until the water from the mushrooms evaporates. Then leave to caramelize over a very low heat for about 5 minutes.

> Add the diced leek flesh, crushed walnuts, salt and pepper then remove from the heat. Fill the leek whites with the mixture and tie them up with cooking string (or prick with a toothpick).

> Heat up the stuffed leeks in a frying pan with the remaining butter over a low heat. If necessary, cover for a few minutes.

> Serve the leeks with any remaining stuffing mixture. Finally, drizzle a dash of walnut oil over them and sprinkle on some sea salt.